title: Rate-limiting step in the metabolism of polar and non-polar monoamines in lung and liver.
abstract: 1 Uptake of the non-hydroxylated amines, [14C]-tryptamine and [14C]-benzylamine in rat lung, infused through the pulmonary circulation, was not saturable over the concentration range 2.5-1,000 microM. 2 The kinetic constants for deamination of a variety of hydroxylated and non-hydroxylated monoamines in liver, perfused via the portal circulation, with monoamine oxidase activity in homogenates of liver were similar. 3 In lung, uptake of both [14C]-tryptamine and [14C]-benzylamine was inhibited by the monoamine oxidase inhibitor deprenyl and competition occurred between tryptamine, benzylamine and beta-phenylethylamine for uptake. 4 These results indicate that tryptamine and benzylamine metabolism in lung is not limited by uptake, unlike that of the hydroxylated amines 5-hydroxytryptamine and noradrenaline and that uptake resembles that of beta-phenylethylamine in lung. 5 the selectivity of the lung in handling monoamines is not shown by the liver, suggesting that lung has a specific role in clearing certain biogenic monoamines.
mesh_terms: D000588:Amines / Q000378:metabolism*; D000818:Animals; D001596:Benzylamines / Q000378:metabolism; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D066298:In Vitro Techniques; D007700:Kinetics; D008099:Liver / Q000378:metabolism*; D008168:Lung / Q000378:metabolism*; D008297:Male; D008928:Mitochondria / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D012642:Selegiline / Q000494:pharmacology; D014363:Tryptamines / Q000378:metabolism
chemical_list: D000588:Amines; D001596:Benzylamines; D014363:Tryptamines; D012642:Selegiline; C030796:benzylamine